Various surfaces are used to facilitate control of a craft's direction while in flight. The ability to control flight characteristics produces a stable flight path and permits controlled guidance of the craft. Flight controls typically include ailerons, an elevator, and a rudder. Flight controls in projectiles however, may be as simple as a set of tail fins to maintain stable flight along a desired path.
Many projectiles are fired or launched through a tube or barrel, necessitating the need for control surfaces that do not impede the projectile's path during launch. To accommodate this requirement, projectiles often utilize deployable control surfaces that extend outwards from the projectile after launch making it necessary to control when and how these control surfaces deploy. Various methods have been used, including explosively actuated or spring loaded control surfaces.